The brake bias valve can cause your symptom.Are the outer part of the brake calipers able to slide in and out freely .Jack it up take a wheel off and get someone to push on the brake pedal while you check for correct movement.Lube the slides so it is easier for calipers to return.a chunck of 4x2 wood is useful if you find them too hard to move by hand

Did you replace master cylinder with correct type?If disc brakes fitted on front, there should not be a check return valve in front supply port.Check supply pressure once brakes have started to hold, loosen one of front bleeders to see if any residual line pressure with pedal released.

Tell us some more! Your answer needs to include more details to help people.You can't post answers that contain an email address.Please enter a valid email address.The email address entered is already associated to an account.Login to postPlease use English characters only.

Check your master cylinder. It could be a piece of junk lodged in the fluid port for the rear brake lines, or in the brake line its self. The fact that both rear wheels spin tells me that if it is a clogged line, it is between the two manifolds, (one next to the master cylinder, and the other where the rear brake line splits into two... one for each rear hub. Or it could be that the piston in the master cylinder needs to be replaced. I would disconnect one brake line at one rear wheel and disconnect the rear brake line at the manifold (near the master cylinder)and blow that line out with air pressure. . do not leave the rear brake line connected to the master cylinder as you blow air through the lines as you may damage the master cylinder piston packings. You'll have to bleed the brakes when you are done.

hello,
It sounds like you have a bad brake problem. smoke from the frt brakes is bad! the following are the things to check and repair.
(1) front brake calipers may be frozen
(2)caliper (rubber lines may be collapsed)
(3) hard lines may have damage?
(4) master cylinder may not be releasing fluid
(5) front calipers may have bolts loose and\or missing

I had the same problem and replaced both calipers with no change, I figured it was the master cylinder. When I pulled off the master cylinder I saw the vacume booster had about 2 cups of brake fluid in it which leaked from the front of the master cylinder. I replaced master cylinder and vacume booster and brakes work great now.

The brake system bleeding procedure differs for ABS and non-ABS
vehicles. The following procedure pertains only to non-ABS vehicles. For
details on bleeding ABS equipped vehicles, refer to the ABS procedures
later in this section.

WARNING
Make sure the master cylinder contains clean DOT 3 brake fluid at all times during the procedure.

The master cylinder must be bled first if it is suspected of containing air. Bleed the master cylinder as follows:

Position a container under the master cylinder to catch the brake fluid.

Loosen the left front brake line (front upper port) at the master cylinder and allow the fluid to flow from the front port.

Connect the line and tighten to 24 ft. lbs. (32 Nm).

Have an assistant depress the brake pedal slowly one time and hold
it down, while you loosen the front line to expel air from the master
cylinder. Tighten the line, then release the brake pedal. Repeat until
all air is removed from the master cylinder.

Tighten the brake line to 24 ft. lbs. (32 Nm) when finished.

Repeat these steps for the right front brake line (rear upper port) at the master cylinder.

WARNING
Do not allow brake fluid to spill on or come in contact with the
vehicle' finish, as it will remove the paint. In case of a spill,
immediately flush the area with water.

If a single line or fitting was the only hydraulic line
disconnected, then only the caliper(s) or wheel cylinder(s) affected by
that line must be bled. If the master cylinder required bleeding, then
all calipers and wheel cylinders must be bled in the proper sequence:

Right rear

Left front

Left rear

Right front

Bleed the individual calipers or wheel cylinders as follows:

Place a suitable wrench over the bleeder screw and attach a clear plastic hose over the screw end.

Submerge the other end in a transparent container of brake fluid.

Loosen the bleed screw, then have an assistant apply the brake
pedal slowly and hold it down. Close the bleed screw, then release the
brake pedal. Repeat the sequence until all air is expelled from the
caliper or cylinder.

When finished, tighten the bleed screw to 97 inch lbs. (11 Nm) for the front, or 66 inch lbs. (7.5 Nm) for the rear.

Check the pedal for a hard feeling with the engine not running. If
the pedal is soft, repeat the bleeding procedure until a firm pedal is
obtained.

Fig. 1: Loosen the front brake line in order to bleed the master cylinder

Fig. 2: Connect a bleed hose from the bleed valve on the front caliper to a jar of brake fluid

Fig. 3: Always follow the lettered sequence when bleeding the hydraulic brake system

check for front brake calipersdragging, if the are replace calipers and front brake hoses, if calipers ok replace master cylinder, This is how to check calipers, jack up front of truck have some one apply brakes and release as soon as they release the brake peddle the wheels should spin freely if not brake the brake line lose at master cylinder if wheels spin free with line loose replace master cylinder, if not replace calipers and hoses.....HOPE THIS HELPS

YOU NEED REMOVE A LITTLE BRAKE FLUID FROM MASTER CYLINDER.THEN YOU RAISE VECHICLE SAFELY.SUPPORT IT WITH JACK STAND.MAKE SURE VECHICLE IS ON LEVEL SOLID GROUND.REMOVE TIRE OR WHEEL.THEN YOU NEED A LARGE C - CLAMP.PLACE C - CLAMP OVER BRAKE CALIPER AND BRAKE SHOE BACKING.TIGHTEN C - CLAMP JUST ENOUGH PUSH CALIPER PISTON BACK IN CYLINDER BORE TO REMOVE CALIPERS FROM ROTORS.TO REMOVE BRAKE CALIPER YOU NEED 2 OPEN AND BOX END WRENCHES ONE TO HOLD CALIPER SLIDE PINS AND THE OTHER WRENCH FOR LOOSEN CALIPER BOLTS.THEN YOU REMOVE CALIPER AND REPLACE FRONT BRAKE SHOES.IF YOU NEED TO REMOVE BRAKE ROTORS JUST REMOVE THE BRAKE CALIPER CARRIER SUPPORT BOLTS THE REMOVE THE BRAKE CALIPER CARRIER SUPPORT THEN REMOVE ROTOR.YOU NEED TO REPLACE BOLTS WITH NEWS AND USE LOCK TIGHT.THEN YOU PUT IN NEW BRAKE PADS IN CALIPER PUT CALIPER BACK ON SUPPORT CARRIER.REPLACE WITH NEW BOLTS USE LOCK TIGHT THEN TORQUE BOLTS TO 26 FT LBS.MAKE SURE MASTER CYLINDER COVER IN PLACE.WHEN YOU FINISH REPLACING BOTH FRONT BRAKE PADS PUMP BRAKE PEDAL TO SEAT BRAKE SHOES AGAINST BRAKE ROTORS SO YOU WILL HAVE FIRM BRAKES WHEN YOU APPLY THEM. THEN CHECK YOUR BRAKE FLUID LEVEL IN MASTER CYLINDER MAKE SURE ITS NOT LOW. MAKE SURE YOU HAVE FIRM BRAKES BEFORE DRIVING.IF YOU HAVE ANY PROBLEMS CHANGING FRONT BRAKE PADS YOU CAN GO TO ANY AUTO PARTS STORE AND BUY A HAYNES REPAIR MANUAL.

Jack up your vehicle. Take the tire off. Use a brake line wrench on the nut at the caliper holding the brake line on. You will lose brake fluid during this process and bleeding of the brakes is recommended after you do this. Once you get the line off the caliper use the brake line wrench on the top nut which holds the line to the vehicle. The old line comes out now. Reverse this process to put the new line it.

Now you need to bleed your brakes. Top off the brake fluid in your master cylinder. Have a helper sit in the vehicle. Have your helper pump the brake pedal 5 to ten times and slowly crack the bleeder screw on on of the wheels. You will see brake fluid come out and possibly some air. Have the helper hold the brake pedal down while you close the bleeder screw. Repeat this procedure until only brake fluid comes out. Repeat procedure on the other three wheels.

1 Siphon off the old brake fluid in the master cylinder reservoir under the hood.2 Fill the reservoir with new brake fluid (don't reuse old fluid as it holds moisture and will corrode your brake system).3 Start with the brake farthest from the Master cylinder, usually rear wheel, passenger side. Pull off the rubber cover on the bleeder valve. Attach the aquarium air line to the nipple on the bleeder.4 Have your assistant pump the brake pedal up and down 3-4 times, then hold the pedal down fairly hard.5 Open the bleeder, let fluid flow out through the air line into a waste container. (preferrably a clear bottle so you can see any air bubbles escaping the system). When the fluid stops and your assistant's foot hits the firewall (brake pedal all the way down), close the bleeder valve immediately!6 Go to step #4 above and drain more fluid out of the bleeder valve until clean fluid comes out. Check the master cylinder every time and top it up as necessary. This procedure uses lots of fluid.7 Now move to the rear brake on the driver's side. Go to step #4 and repeat the same procedures above until clean fluid comes out of the bleeder valve and no bubbles.8 Next is the front brake, passenger side, same procedure. Then the drivers side and the same procedure.9 When finished check for any leaks, remount rubber covers on the bleeder valve nipples. Remount all wheels, re-torque lug nuts after 50-100 miles of driving.10 Start vehicle and depress the brake pedal. It should feel much less spongy than before this procedure. If not, there is air in the system, start over. Bleed everything again.Note: if you assistant releases the brake pedal before you can close the bleeder valve then air will be introduced into the brake lines. This is no good! Before you start tell your assistant you will tell him/her PUMP, HOLD DOWN, RELEASE commands.That's it, you're done. Congratulate yourself on saving some cash instead of handing it over to a mechanic.

Well I don't think you'll need to buy parts,it sounds like there may be sludge built up between the master cylinder and the proportional valve to the front brakes.Pull the valve off(follow the line off the master cylinder and you'll find the valve)clean it and then flush/bleed the master cylinder before you reinstall,Then flush/bleed the rest of the system.There's a relly good chance that may be all you need to do,but you may need to pull the calipers and clean them also.Comment back if you need more help,Good Luck(To)Yotaguy